A wide variety of machinery is available for stranding continuous filaments, for example, stranded metal wire of the type which subsequently is insulated for use in electrical installations. Such operations have been performed in the past on machines in which the spools of wire were rotated about a central core wire to produce a so-called concentric strand configuration. By a "concentric" strand is meant one wherein the strands of each successive layer surrounding the core wire rest side-by-side, and have some back-twist to reduce the tendency of the strand of wires to open up. The mechanical and dynamic problems inherent in such machines include relatively high centrifugal forces and high friction forces, which limit operating speeds and necessitate reinforced and complex structures. Additionally, the finished product tends to be difficult to control as to surface condition, and uniformity of size and weight. Such considerations have led to the use of other means to produce stranded wire. For example, so-called bunchers, particularly of the "reverse twist" type, have been modified to guide the constituent wires into the geometric configuration of a concentric strand, rather than the comparatively random configuration of a bunch strand. However, the products of such operations exhibit characteristics which are deemed undesirable in the industry. For example, insufficient back-twist in the individual strands to ensure dynamic retention of the constituent wires in place, and damage to the constituent wires caused by the dies that are used to effect closure of the wires and monitoring of the overall diameter of the finished strand, are objectionable results of such processes, and are among the reasons for the better alternative having been sought in other apparatus. The so-called "barrel strander" overcomes these objections. In such machines, a row of spools each containing a single continuous end of wire, all of which are single ended spools, or one or more of which may be a multi-ended, previously stranded continuum, are gimble-mounted on support bearings along the central axis of an apertured outer cylinder, so that the latter may revolve about them while they remain relatively stationary. The wires may then be paid off from the spools through pulleys arrayed on the inside of the cylinder, through a closure die to a take-up reel for the finished strand. However, in order to achieve the high barrel rotation speeds which are a necessary concomitant of the high production rates which are desired, it is necessary to minimize as far as possible the weight and diameter of the barrel, so that centrifugal forces will be minimized as well. Correspondingly, this presents engineering problems in accomodating spools of individual size such that comparatively long strands may be produced, and in mounting them in tandem down the length of the axis of the interior of the barrel. The result is that machinery of this type does not lend itself to the production of materials which are susceptible to deformation as a consequence of the resulting torsional and friction forces. This happens, for example, on finer strands made from malleable material such as copper, causing the quality, size, weight, surface, and electrical variations which result not to be up to standards desired by industry. Further, in the use of stranders of the barrel type, when an individual spool of wire runs out, it is an industry practice to connect the end of the wire on the spent spool to the beginning of the wire on a replacement spool. This is done by silver-soldering the two together or utilizing other connection means, which can be tedious and time-consuming to perform. The structural configuration, and size limitations of such machines render alternative procedures impractical.
In my previous patent application Ser. No. 96,140, filed Nov. 20, 1979 and now U.S. Pat. No. 4,302,924, I disclosed apparatus which overcomes many of the drawbacks of prior art devices, while, at the same time, is capable of producing products having commercially acceptable, and in some cases improved, characteristics. However, as a further improvement, I have found it desirable to find means to fulfill a number of additional objectives, including to further reduce the size and weight of such apparatus, to reduce the weight and force bearing requirements of the components of such apparatus, to increase the speed of such machines, to reduce or eliminate tension problems on the individual wires being stranded, to reduce the probability of individual wire breakage, to reduce the machine down-time due to such things as discontinuities in the length of wires as between spools, and to achieve other desired objectives.
Accordingly, it is an object of this invention to provide means to produce a configuration of continuous filaments, such as wires that will enable achievement of the foregoing objectives.
Another object of the present invention is to provide such means to minimize weight, diameter, resistivity, and surface variations in the production of articles made from comparatively deformable materials.
Still another object is to provide stranding means in which changeovers in direction and/or lay-length may be easily changed.
Another object is to produce such means which are easier to load than prior art strading machines.
Yet another object is to satisfy the foregoing objectives with means which have low weight and simple construction, to minimize centrifugal and other dynamic forces when the machine is in operation and to facilitate access to its various constituent parts for its operation and maintenance.
Still another object of this invention is to provide means for satisfying the foregoing objectives wherein the multiplicity of wire-ends being used may be changed simultaneously by changing a single spool.